Solid-state electroluminescent (EL) lighting devices made of area-emissive light-emitting diodes, both organic and inorganic are increasingly useful for applications requiring robustness and long-life. Such solid-state lighting devices are of great interest because they provide a light-emitting area rather than a point source of light (as is found in inorganic light-emitting diodes formed in crystalline semiconductors). This attribute of EL lighting devices reduces the maximum heat of the device, facilitates efficient extraction of light from the diodes in a lighting fixture or luminaire, and provides large-area diffuse illumination sources, which are preferred in many environments to reduce eye strain and provide a comfortable viewing environment. To obtain these advantages, it is desirable that the luminaire have a large area, typically greater than 200 cm2 and often well in excess of 3000 cm2.
Organic EL devices, such as organic light emitting diodes (OLEDs), can be manufactured by depositing materials on a substrate and encapsulating them with a cover or layer. This process enables the creation of single, monolithic lighting elements on a single substrate. Such substrates can be removably inserted into a socket and controlled, for example, by a light switch mounted on a wall or on a lamp fixture. Alternatively, a control switch can be mounted directly in a socket, for example as taught in U.S. Pat. No. 6,819,036.
During the deposition process, very thin layers of light-emitting materials, often on the order of 10 s or 100 s of nm in thickness, are deposited between pairs of electrodes. Because of the very small distance between these electrodes, shorts can occur between the electrodes. These shorts can be immediately visible but can also form over time and can prevent a lamp from functioning entirely, reduce the luminance of the lamp, or detract from its appearance.
Intelligent and sophisticated control systems for lighting are known in the industry. For example, U.S. Pat. No. 7,521,667 includes references to inorganic, point-source LED lamps having a sensor. U.S. Pat. No. 7,265,332 describes a light monitor and lighting control system and discusses inexpensive, miniaturized light monitoring systems and control systems useful in large-building lighting networks. WO2009/060373 discusses optical communication in which an OLED can serve as an emitter and a sensor. U.S. Pat. No. 7,386,421 discloses a lighting control system for optimizing area illumination at a desired position. U.S. Pat. No. 6,791,824 describes an outdoor lighting control system for an outdoor lighting system network for automatically sensing, conveying, and recording data relevant to the operation of the lighting system network so that both control and maintenance can be performed more efficiently. At each of plural lamp locations in the network, there is a controller module that receives electric power input and that supplies electric power to the remaining lamp locations. Each controller module has a first relay to deliver current to one or more outdoor illumination lamps at the controller module's location and a second relay for switching electric power on to a succeeding lamp location. A first current sensor monitors current to the lamps at each lamp location, and a second current sensor monitors current to the remaining locations.
Such control methods for flat-panel area-emissive lighting are useful, but the switch mechanisms conventionally employed in lighting can be large and relatively expensive. Furthermore, typical lamps employing OLED materials employ a plurality of emissive elements on a single substrate, to improve the robustness of the lamp. It can be advantageous to separately control different light-emitting elements, or groups of electrically-connected light-emitting elements, that are all formed on a single substrate as taught in U.S. Pat. No. 6,680,578. Techniques to do so can require an excessive number of external connections to the substrate, wiring to the lamp, and switches. Moreover, the use of sensors and sophisticated control mechanisms to provide intelligent lighting can create complex and expensive wiring circuits and sensors in buildings that employ intelligent lighting control systems.
In view of the foregoing, it is therefore an object of the present invention to provide an improved control device for flat-panel, area-emissive lighting that provides a high level of integration at reduced manufacturing cost, intelligent control, and reduced infrastructure requirements.